From: Rob Landley <rob@landley.net>
Organization: Boundaries Unlimited
To: Jason Lunz <lunz@acm.org>
Subject: Re: [PATCH] mtd: allow mtd and jffs2 when ARCH=um
Date: Tue, 14 Dec 2010 18:40:25 -0600
User-Agent: KMail/1.11.2 (Linux/2.6.28-19-generic; KDE/4.2.2; x86_64; ; )
Cc: Artem Bityutskiy <dedekind1@gmail.com>,
        "richard -rw- weinberger" <richard.weinberger@gmail.com>,
        Sam Ravnborg <sam@ravnborg.org>, David Woodhouse <dwmw2@infradead.org>,
        atom ota <atomota@sleepyhammer.com>,
        user-mode-linux-devel@lists.sourceforge.net,
        Jeff Dike <jdike@addtoit.com>, lkml <linux-kernel@vger.kernel.org>,
        linux-mtd@lists.infradead.org
References: <20071024011712.GA3762@falooley.org> <1292356893.29257.1.camel@koala> <20101214212349.GA6937@falooley.org>
In-Reply-To: <20101214212349.GA6937@falooley.org>
MIME-Version: 1.0
Content-Type: Text/Plain;
  charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
Message-Id: <201012141840.27529.rob@landley.net>
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1553
Lines: 30

On Tuesday 14 December 2010 15:23:49 Jason Lunz wrote:
> On one hand you've got uml, which simply doesn't have mmio. On the other
> there's mtd, which began as a method for accessing hardware devices that
> are often accessed using mmio. But then the mtd subsystem developed
> emulations of that hardware that are software based and thus don't
> require mmio. It's mainly these emulated backends I'm interested in
> exposing.
>
> Nothing is going to change so that it makes sense to have any real
> mmio-using hardware driver run on uml. The question you raise is, are
> there other classes of driver with a software-only subset that can be
> exposed on uml? And if so, would adding stub implementations of
> readb/writeb and friends actually be enough to make those work? I'm not
> aware of any, so at present I don't think the argument for implementing
> this in uml arch code is very strong. Or in other words, I don't think a
> "general solution" would be very general.

For what it's worth, QEMU had replaced all my use cases for UML in the past 
few years.  If I wanted to play with loopback mounting jffs2 I'd build a kernel 
to run under QEMU, and have that emulate the flash.

Rob
-- 
GPLv3: as worthy a successor as The Phantom Menace, as timely as Duke Nukem 
Forever, and as welcome as New Coke.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/